- Think of your car like a computer. You can’t just hit the power button on a computer and then immediately start clicking on things and hitting keys. The computer has to go through it’s start up procedure before you can do anything. Your car is the same way. The 02 sensors need to warm up and come online before the ECU can read the AFR and the AVCS needs to go through it’s calibration procedure to make sure the cams are aligned. Driving the car without the 02 sensors reading or the cams activated can cause the fueling to be way off from it’s desired target and the turbo will also spool 500-1000 rpm slower without the AVCS activated. Both of these things happen every time you start the car, not just after a flash.
02 SENSOR WARM-UP
- After you start the car it takes the front 02 sensor 60-90 seconds to warmup, even if the car is warm. So it’s best not to just start your car and start beating on it because the AF learning and corrections may not be active. You can monitor this by monitoring AF Sensor 1 Ratio on the AP. When you first start the car the AFR will stick at 14.7 until the 02 sensor has warmed up. Once the AFR has moved from 14.7 and the AF Correction1 are AF Learning1 are active, then you know it’s ok to log. You need to be careful about beating on the car before the sensor is active, running lean will cause knock and could potentially blow the motor. You can see an example of a non-warm 02 sensor below...the AFR sticks to 14.7 until 5800rpm. Once the 02 Sensor turns on you will likely see very large negative AF Corrections/Learning on the AP -30 to -40%. This is perfectly normal. The cars need lots of fuel for cranking and post start enrichment, especially in cold temps. Since the 02 sensor isn’t active, there isn’t any way for the ECU to monitor the AFR, so Subaru errs on the side of cause and runs the cars rich and then lets the 02 sensor correct the fueling during warmup. If the cars are lean during cranking on coldstarts, they usually just won’t start. So being richer is better. The corrections will gradually make there way towards zero as the coolant temp increases. The closer the coolant temp is to 140 degrees the less time it will take the corrections to move towards zero. If you’re down at 30 degree coolant temp, then the high corrections will take a while to get to zero.
** YOU WILL LIKELY NEVER SEE THIS CALIBRATION UNLESS YOUR AP IS POWERED AND ON THE GAUGE SCREEN BEFORE YOU START THE CAR. **
- The AVCS also has to go through a warmup/activation procedure for 10-15 seconds any time you start the car.
- The coolant temp also has to be 160*+ for the calibration to happen.
- You can monitor the calibration by watching AVCS Intake Left or Right. It will go -5, -4, -3 -2, -1, 0, 1, 2, 3, 4, 5, then back to zero.
- This process has to take place at idle, if you start driving before the AVCS is active, it won’t become active during the drive unless you stop and idle long enough for it to take place.
- To check if AVCS is active:
IDLE FLUCTUATIONS DURING WARM-UP
- During startup the stock mapping retards the timing to -15* which can cause idle fluctuations at various times during cold starts. These timing maps are not defined in the Cobb software. After a period of time, the timing will jump up to 5-10*…this timing jump causes an rpm fluctuation. Once the 02 sensor comes online, it can also cause an rpm fluctuation. So there are 2-3 periods during startup that may cause an rpm fluctuation that simply can’t be tuned out at this time. - After flashing a map, you have to cruise for a bit to get the temps down. Otherwise your intake temps will be really high. You basically can't be stopped on the side of the road with the car idling and just take off and start beating on the car. You have to cruise to get the temps down. Otherwise everything will be heat soaked and the car will just knock all the time
Video showing the AVCS activation procedure
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